perf: otimizar dashboard com indexes, cache e consolidação de queries (v1.3.0)

- Adicionar indexes compostos em lancamentos para queries frequentes
- Eliminar ~20 JOINs com pagadores via helper cacheado getAdminPagadorId()
- Consolidar queries: income-expense-balance (12→1), payment-status (2→1), categories (4→2)
- Adicionar cache cross-request via unstable_cache com tag-based invalidation
- Limitar scan de métricas a 24 meses
- Deduplicar auth session por request via React.cache()

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/pagadores/get-admin-id.ts

@@ -0,0 +1,25 @@
+import { and, eq } from "drizzle-orm";
+import { cache } from "react";
+import { pagadores } from "@/db/schema";
+import { db } from "@/lib/db";
+import { PAGADOR_ROLE_ADMIN } from "@/lib/pagadores/constants";
+
+/**
+ * Returns the admin pagador ID for a user (cached per request via React.cache).
+ * Eliminates the need for JOIN with pagadores in ~20 dashboard queries.
+ */
+export const getAdminPagadorId = cache(
+	async (userId: string): Promise<string | null> => {
+		const [row] = await db
+			.select({ id: pagadores.id })
+			.from(pagadores)
+			.where(
+				and(
+					eq(pagadores.userId, userId),
+					eq(pagadores.role, PAGADOR_ROLE_ADMIN),
+				),
+			)
+			.limit(1);
+		return row?.id ?? null;
+	},
+);